1. Field of the Invention
The invention relates generally relates to an optical system, and more particularly, to an optical imaging system.
2. Description of Related Art
Imaging lenses are one of the most important components in optical systems such as video cameras, digital cameras, projectors, microscopes, and endoscopes. Due to cost considerations, typically spherical glass lenses are adopted for the lenses of an imaging lens. The formed images are not totally equivalent to the original objects because of the added effects of phase differences, diffraction, and dispersion for the optical paths of the optical systems result, which result in image aberrations.
In order to achieve preferable imaging effects, optical design engineers have conventionally begun with the lenses themselves, for instance by adopting aspheric lenses, cemented lenses, or by specifically designing each curvature of the lenses for preferred combinations. However, the use of aspheric lenses drastically increases the manufacturing cost, the design complexity, and the optical system sensitivity. Therefore, professional photographers frequently spend extraordinary amounts of money to purchase expensive lenses.
Moreover, when the imaging lens is applied in medical equipments (e.g., fundus cameras or endoscopes examining the mouth and throat), because the human anatomy for areas such as the fundus oculi, the throat, and the mouth are extremely three-dimensional, very close shooting with the lenses result in a shallow depth of field. Therefore, in an image it is difficult to clearly present structures of different distances from the lens. When shot over a plurality of photographs, then a comparison between the different structures becomes difficult.
Additionally, when using conventional imaging cameras, a resolution of the optical system is limited by a choice of an imaging lens. Hence, adaptive adjustments of resolution for different user requirements cannot be made.